Conventionally, there is known a technique in which a diesel particulate filter (oxidation catalyst, honeycomb filter) is disposed in an exhaust gas path of a diesel engine as an exhaust gas purification device (post-processing device), so as to purify exhaust gas from the diesel engine by the diesel particulate filter (see Patent Document 1). In addition, there is a technique in which an exhaust gas purification device is mounted on a vehicle body frame with a diesel engine (see Patent Document 2, Patent Document 3, and Patent Document 4). Further, there is also a technique in which a freezing air conditioning unit and an engine for driving the air conditioning unit are mounted in a container for transporting frozen cargo or the like, inside temperature of the container is maintained at a temperature necessary for freezing preservation of the cargo (for example, −20° C.) or lower, and the container is linked to a tractor, so as to transport the cargo in frozen preserved state (Patent Document 5).